1. Field of the Invention
The present invention relates to an apparatus for identifying tools and for managing tool data and, more particularly, to a tool identifying (or discriminating) apparatus which is used in machine tools such as machining center and the like having an automatic tool changing (or exchanging) apparatus and used to discriminate the kinds of tools held in each of tool holders and also to a tool data managing apparatus for storing various data regarding the tools and for managing the tools.
2. Prior Art Statement
In a conventional machining center having an automatic tool changing apparatus, a number of tools are respectively fixed to the tool shanks (tool holders) and held in the tool magazine or tool pot (tool keeping or accommodating means) provided in the machining center. When exchanging the tools in accordance with the machining of a workpiece, the tool magazine is rotated and when a desired tool shank reaches the position to change the tools, the rotation of the tool magazine is stopped. The tool fixed to the spindle (main shaft) of the machining center is removed together with its tool shank. Then, the new (desired) tool shank is taken out from the tool magazine by the exchanging arm to insert it into and fix to the spindle of the machining center and the machining is continued. Therefore, prior to using the machine tool, the data regarding the tools such as the kinds of tools supported in the tool magazine, the diameters of tools (for example, drill diameters), the lengths of tools (e.g., drill lengths), the offset amounts of tools, and the like needs to be previously stored into the memory of the control unit of the machine tool by use of the data input apparatus.
The above conventional machine tool has the disadvantage such that it takes a long time to input the data concerned with the tools. There is also the problem such that if the data was erroneously input or the tool shank was inserted to the improper position of the tool magazine, in the case of taking out the tool shank at that wrong position and performing the work, a desired work cannot be executed. On the other hand, in the case of machining in accordance with the numerical control program, the machining position is corrected for every tool by use of the offset amount and the like. However, there is the problem such that each time the tool of the tool shank is changed, the correction value needs to be input into the numerical control unit.
Further, as ways for managing the tool shanks in machine tools, the fixed address system and the variable address system are known. Namely, in the fixed address system, each tool shank is kept at a predetermined position peculiar to each tool shank in the tool magazine. In the variable address system, the control unit of the machine tool stores the keeping position in the tool magazine in connection with each tool shank, thereby enabling each tool shank to be held at an arbitrary position of the tool magazine. When a number of tool shanks are supported in the tool magazine, it is preferable to use the latter system in which in order to promptly exchange the tools, the tool shanks are not fixedly concerned with the keeping positions of the tool magazine in a one-to-one corresponding manner, but the positions of the tool shanks are stored in connection with the kinds of tools in the memory of the control unit of the machine tool.
However, in the case of managing the tool shanks by such system, there is the problem such that the constitution of the apparatus becomes complicated since the backup of the memory and the like are necessary. There is also the problems such that if the tool data which has once been stored is erased due to some reasons, the tool data must be input again. Further, if the sensor to detect the movement of the tool magazine erroneously detects it or if the apparatus to rotate the tool shanks erroneously operates, there will be the risk such that the tool shank of the tool different from the designated tool is taken out of the tool magazine and the machining is performed by the improper tool.
Moreover, in a large-scale machining center and the like, in order to manage the lifetime of each tool, the use time of each tool is measured by the numerical control unit and the tools which have reached the lifetimes are automatically changed. In this case as well, there is also the disadvantage such that when the tool (tool shank) is taken out of the tool pot, the use time of the tool until now needs to be recorded on a record note and the like and when it is again inserted into the tool magazine, the use time of this tool must be reinput into the control unit.